Separation system of metal powder from slurry and process

ABSTRACT

A system and method of separating metal powder from a slurry of liquid metal and metal powder and salt is disclosed in which the slurry is introduced into a first vessel operated in an inert environment when liquid metal is separated from the metal powder and salt leaving principally salt and metal powder substantially free of liquid metal. The salt and metal powder is transferred to a second vessel operated in an inert enviroment with both enviroments being protected from contamination. Then the salt and metal powder substantially free of salt and liquid metal. The method is particularly applicable for use in the production of Ti and its alloys.

BACKGROUND OF THE INVENTION

This invention relates to a separation system and process as illustratedin FIG. 1 useful for the product produced by Armstrong method asdisclosed and claimed in U.S. Pat. Nos. 5,779,761; 5,958,106 and6,409,797, the disclosures of each and every one of the above-captionedpatents are incorporated by reference.

SUMMARY OF THE INVENTION

A principal object of the invention is to provide a separation systemfor the Armstrong process disclosed in the '761, '106 and '797 patents;

Another object of the invention is to provide a continuous separationsystem.

The invention consists of certain novel features and a combination ofparts hereinafter fully described, illustrated in the accompanyingdrawings, it being understood that various changes in the details may bemade without departing from the spirit, or sacrificing any of theadvantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the separation system of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The system 10 of the present invention deals with the separation of ametal, alloy or ceramic product, such as titanium, for example only,from the reaction products in the Armstrong process. Although theArmstrong process is applicable to a wide variety of exothermicreactions, it is principally applicable to metals, mixtures, alloys andceramics disclosed in the above-mentioned patents. The product ofArmstrong process is a slurry of excess reductant metal, product metaland alloy or ceramic and salt produced from the reaction. This slurryhas to be separated so that various parts of it can be recycled and theproduced metal, alloy or ceramic separated and passivated if necessary.

Turning now to the schematic illustration of the system and process ofthe present invention illustrated in FIG. 1, there is disclosed in thesystem 10 a source of, for illustration purposes only, titaniumtetrachloride 12 which is introduced into a reactor 15 of the typehereinbefore disclosed in the Armstrong process. A supply tank orreservoir 17 with a supply of sodium (or other reductant) 18 istransferred by a pump 19 to the reactor 15 wherein a slurry product 20of excess reductant and metal, alloy or ceramic, and salt is produced atan elevated temperature, all as previously described in the incorporatedpatents.

The slurry product 20 is transferred to a vessel 25 which is in theillustration dome-shaped, but not necessarily of that configuration, thevessel 25 having an interior 26 into which the slurry product 20 isintroduced. A filter 27, preferably but not necessarily cylindrical, ispositioned within the interior 26 and defines an annulus 28, the slurryproduct 20 being received inside the cylindrical filter 27. An annularheat exchanger 29 is positioned around the vessel 25, all for a purposehereinafter disclosed.

The vessel 25 further includes a moveable bottom closure 30. Heatexchange plates 32 are connected as will hereinafter be described to anisolated heating system 50. A collection vessel 35 is positioned belowthe vessel 25 and is sealed therefrom by the moveable bottom closure 30.The collection vessel 35 has an inwardly sloping bottom surface 36 whichleads to a crusher 38 and a valve 39 in the outlet 40 of the collectionvessel 35.

Finally, a vapor conduit 42 interconnects the top of the vessel 25 andparticularly the interior 26 thereof with a condenser vessel 45, thecondenser vessel having a heat exchange plate 46 connected, ashereinafter described, to an isolated cooling system 60. The condenser45 is connected to a condenser reservoir 49, the condensate collectedtherein being routed to the sodium supply tank or reservoir 17.

The isolated heating system 50 includes a head tank 52 for the heatingfluid which is moved by pump 53 to the heater 55 as will be hereinafterdescribed, connected to both the heat exchanger 29 surrounding thevessel 25 and the heat exchange plates 32 interior of the vessel 25. Theisolating cooling system 60 also is provided with a head tank 62, a pump63 and a cooler 65 which serves to cool the cooling fluid circulated inan isolated loop to the cooling plates 46 as will be hereinafter setforth.

Below the valve 39 and the collection vessel 35 is a product conveyor 70having a baffle or cake spreader 71 extending downwardly toward theconveyor 70. The conveyor 70 onto which the produced metal, alloy orceramic and salt are introduced from the collection vessel 35, afterremoval of the excess reductant metal, is contacted with a countercurrent flow of gas, preferably but not necessarily oxygen and argon, 77from a blower 75 in communication with a supply 76 of oxygen and thesupply of inert gas such as argon. The heat exchanger 79 is incommunication with the blower 75 so as to cool the oxygen/argon mixture77 as it flows in counter current relationship with the produced metal,alloy or ceramic on the conveyor 70, thereby to contact the productparticulates with oxygen to inertthe produced metal, alloy or ceramicwhen required but not so much as to contaminate the produced material.

As indicated in the flow sheet of FIG. 1, there are a plurality of flowmeters 81 distributed throughout the system, as required and as wellknown in the engineering art. There are pressure transducers 86 andpressure control valves 89 where required, all within the engineeringskill of the art. A back filter valve 91 is provided in order to flushthe filter 27 if necessary. Additionally, a variety of standard shut-offvalves 93 are positioned within the loop, hereinafter to be explainedand as required. A vacuum pump 95 is used to draw a vacuum in the vessel25, as will be explained, and the symbol indicated by reference numeral100 indicates that a plurality of the same or similar systems may beoperating at any one time, it being remembered that the enclosed figureis for a single reactor 15 and one separation vessel 25, wherein as in acommercial production plant, a plurality of reactors 15 may be operatingsimultaneously each reactor 15 may have more than one separation vessel25, all depending on engineering economics and ordinary scale up issues.

Product 20 from the reactor 15 exits through line 110 and enters vessel25 at the top thereof. Although line 110 is shown entering above thefilter 27, preferably the line 110 and filter 27 are positioned so thatslurry 20 is introduced below the top of filter 27 or in the center ofthe filter or both. As described in the previously incorporated patents,the slurry product 20 consists of excess reductant metal, salt formed bythe reaction and the product of the reaction which in this specificexample is titanium existing as solid particles. The product 20 inslurry form from the reactor 15 is at an elevated temperature dependingon the amount of excess reductant metal present, the heat capacitythereof and other factors in the reactor 15 during operation of theArmstrong process. In the vessel 25 is a filter 27 which occupies aportion of the interior 26 of the vessel 25, the interior optionallybeing heated with the annular heat exchanger 29. The slurry product 20is directed to the interior of the filter 27 where the slurry contactsthe heat exchange plates 32.

In the heating system 50, the heat exchange fluid in the plates 32 passwith the heat exchange fluid from the annular heat exchanger 29 throughline 111 to the line 112 which connects the heat exchange medium supplyin the head tank 52 to the heat exchanger 55. Fluid moves from theheater 55 through the heat exchange plates 32 by means of the pump 53 asthe heated heat exchange fluid flows out of the heat exchanger 55through line 113 and back into the heat exchange plates 32 and/or theannular heat exchanger 29. Because the heating system 50 is a closedloop, the heat exchange fluid may or may not be the same as thereductant metal used in the reactor 15. NaK is shown as an examplebecause of the low melting point thereof, but any other suitable heatexchange fluid may be used. Suitable valves 93 control the flow of heatexchange fluid from the heater 55 to either or both of the heatexchanger 29 and plates 32. Preferably, the plates 32 are relativelyclose together, on the order of a few inches, to provide more heat tothe cake which forms as excess reductant metal vaporizes. Moreover,closer plates 32 reduce the path length the heat has to travel and thepath length the excess reductant metal vapor travels through the formingcake, thereby to reduce the time required to distill and remove excessreductant metal from the vessel 25. Exact spacing of the plates 32depends on a number of factors, including but not limited to, the totalsurface area of the plates, the heat transfer coefficient of the plates,the amount of reductant metal to be vaporized and the temperaturedifferential between the inside and the outside of the plates.

When the slurry product 20 comes out of the reactor 15, it is at apressure at which the reactor 15 is operated, usually up to about twoatmospheres. The product slurry 20 enters the inside of filter 27 underelevated pressure and gravity results in the liquid reductant metalbeing expressed through the filter 27 into the annular space 28 and fedby the line 120 into the reservoir 17. The driving force for thisportion of the separation is gravity and the pressure differentialbetween the reactor 15 and the inlet pressure of pump 19. If requiredthe annulus 28 may be operated under vacuum to assist removal of liquidreductant metal, or the pressure in vessel 25 may be increased duringthe deliquoring of the reductant metal. After sufficient liquid metalhas drained through the filter 27 by the aforementioned process, the PCVvalve 89 is closed and other valves 93 are closed to isolate vessel 25and then the valve 93 to the vacuum pump 95 is opened, whereupon avacuum is established in the interior 26 of vessel 25. Heating fluid(liquid or vapor, for instance Na vapor) is directed into the heatexchanger plates 32 to boil the remaining reductant metal 18 producing afilter cake. The temperature in vessel 25 is elevated sufficiently tovaporize remaining liquid metal reductant 18 therein which is drawn offthrough conduit 42 to the condenser 45. The conduit 42 is required to berelatively large in diameter to permit rapid evacuation of the interior26 of the vessel 25. Because the pressure drop between the vessel 25 andthe condenser 45, during vaporization of the reductant metal 18 is low,the specific volume is high and the mass transfer low, requiring a largediameter conduit 42. Boiling the reductant metal on the shell side isaccomplished by heat exchange with a heated fluid on the tube side.

The annular heat exchanger 29 is optionally operated to maintain theexpressed liquid in the annulus 28 at a sufficient temperature to floweasily and/or to provide additional heat to the vessel 25 to assist invaporization of excess reductant metal from the interior 26 thereof.After liquid metal reductant vapor has been removed from the interior 26of the vessel 25, a filter cake remains from the slurry 20. Theappropriate valves 93 are closed and the vacuum pump 95 is isolated fromthe system.

In the condenser 45, heat exchange plates 46 are positioned in order tocool the reductant metal vapor introduced thereinto. The cooling system60 is operated in a closed loop and maintained at a temperaturesufficiently low that reductant metal vapor introduced into thecondenser 45 condenses and flows out of the condenser, as will bedisclosed. The cooling system 60 includes a cooler 65 as previouslydescribed and the pump 62. The coolant exits from the cooler 65 throughline 114 which enters the heat exchange plates 46 and leaves through aline 115 which joins the line 116 to interconnect the head tank 62 andthe cooler 65. As seen in the schematic of FIG. 1, the heat exchangefluid used in the heating system 50 and the cooling system 60 may be thesame or may be different, as the systems 50 and 60 can be maintainedseparately or intermixed.

Both the vessel 25 and the condenser 45 are operated at least part ofthe time under a protective atmosphere of argon or other suitable inertgas from the argon supply 85, the pressure of which is monitored by thetransducer 86, the (argon) supply inert gas 85 being connected to thecondenser 45 by a line 117, the condenser 45 also being in communicationwith the vessel 25 by means of the oversized conduit 42. Further, as maybe seen, each of the heating system 50 and the cooling system 60 isprovided with its own pump, respectively 53 and 63. As suggested in theschematic of FIG. 1, the heating and cooling fluid may, preferably beNaK due to its lower melting point, but not necessarily, and as analternative could be the same as the reductant metal in either liquid orvapor phase, as disclosed.

After sufficient reductant metal 18 has been removed from the slurry 20,via the filter 27 and the conduit 42, remaining therein is a combinationof the titanium product in powder form and salt made during theexothermic reaction in reactor 15. Because the resultant dried cake hasa smaller volume than the slurry product 20 introduced, when the movablebottom closure 30 is opened, the dry cake falls from the filter 27 intothe collection vessel 35 whereupon the combination of salt and titaniumfall into the crusher 38 due to the sloped bottom walls 36. In the eventthe cake does not readily fall of its own accord, various standardvibration inducing mechanism or a cake breaking mechanism may be used toassist transfer of the cake to the collection vessel 35. The collectionvessel 35 as indicated is maintained under an inert atmosphere at aboutatmospheric pressure, and after the cake passes through the crusher 38into the exit or outlet 40, the cake passes downwardly through valve 39onto the conveyor 70. There is a cake spreader or baffle 71 downstreamof the valve 39 which spreads the cake so that as it is contacted by amixture 77 of inert gas, preferably argon, and oxygen flowingcounter-current to the direction of the product, the titanium powder ispassivated and cooled. Although the conveyor 70 is positioned in FIG. 1horizontally, it may be advantageous to have the conveyor move upwardlyat a slant as a safety measure in the event that closure 30 fails, thenexcess reductant metal would not flow toward a water wash. In addition,there may be cost advantages in having the product wash equipment on thesame level as the separation equipment.

Cooling and passivating is accomplished in the cooler 79 with blower 75which blows a cooled argon and oxygen mixture through a conduit 121 tothe product, it being seen from the schematic that the counter-currentflow of argon and oxygen with the product has the highest concentrationof oxygen encountering already passivated and cooled titanium so as tominimize the amount of oxygen used in the passivation process. Oxygen isconducted to the system from a supply thereof 76 through a valve 93 andline 122 and is generally maintained at a concentration of about 0.1 toabout 3% by weight. The mixture of passivated titanium and salt isthereafter fed to a wash system not shown. Various flow meters 81 arepositioned throughout the system as required, as are pressure controlvalves 89 and pressure transducers 86. A filter backwash valve 91 ispositioned so that the filter 27 can be backwashed when required if itbecomes clogged or otherwise requires backwashing. Standard engineeringitems such as valves 93, vacuum pump 95 and pressure transducers 86 aresituated as required. Symbol 100 is used to denote that parallel systemsidentical or similar to all or a portion of the system 10 illustratedmay be operated simultaneously or in sequence.

In the Armstrong process, the production of the metal, alloy or ceramicis continuous as long as the reactants are fed to the reactor. Thepresent invention provides a separation system, apparatus and methodwhich permits the separation to be either continuous or in sequentialbatches so rapidly switched by appropriate valving as to be ascontinuous as required. The object of the invention is to provide aseparation apparatus, system and method which allows the reactor(s) 15in a commercial plant to operate continuously or in economic batches.Reduction of the distillation time in vessel 25 is important in order tooperate a plant economically, and economics dictate the exact size,number and configuration of separation systems and production systemsemployed. Although described with respect to Ti powder, the inventionapplies to the separation of any metal, alloy thereof or ceramicproduced by the Armstrong process or other industrial processes.

The heating mechanism shown is by fluid heat exchange, but heaters couldalso be electric or other equivalent means, all of which areincorporated herein. The bottom closure 30 is shown as hinged and isavailable commercially. The closure 30 may be clamped when shut andhydraulically moved to the open position; however, sliding closures suchas gate valves are available and incorporated herein. Although thereactor 20 is shown separate from the vessel 25, the invention includesengineering changes within the skill of the art, such as but not limitedto incorporating reactor 20 into vessel 25. Although vessel 35 isillustrated in one embodiment, the vessel 35 could easily be designed asa pipe. Also, the crusher 38 could be located in vessel 25 orintermediate vessel 25 and vessel 35. Moreover, the cake forming on thefilter 27 may be broken up prior to or during or subsequent to removalof the liquid metal therefrom. Similarly, when referring to an inertenvironment, the invention includes a vacuum as well as an inert gas. Animportant feature of the invention is the separation of vessels 25 and35 so the environments of each remain separate. That way, no oxygen cancontaminate either vessel.

In one specific example, a reactor 15 producing 2 million pounds peryear of titanium powder or alloy powder requires two vessels 25, eachroughly 14′ high and 7′ in diameterwith appropriate valving, so that thereactor 15 would operate continuously and when one vessel 25 was filled,the slurry product from the reactor would switch automatically to thesecond vessel 25. The fill time for each vessel 25 is the same orsomewhat longer than the deliquor, distill and evacuation time forvessel 25.

Changing production rates of reactor 15 simply requires engineeringcalculations for the size and number of vessels 25 and the relatedequipment and separation systems. The invention as disclosed permitscontinuous production and separation of metal or ceramic powder, whilethe specific example disclosed permits continuous separation with two orat most three vessels 25 available for each reactor 15. With multiplereactors 15, the number of vessels 25 and related equipment wouldprobably be between 2 and 3 times the number of reactors.

While there has been disclosed what is considered to be the preferredembodiment of the present intention, it is understood that variouschanges in the details may be made without departing from the spirit, orsacrificing any of the advantages of the present invention.

1. A method of separating metal powder from a slurry of liquid metal andmetal powder and salt, comprising introducing the slurry into a firstvessel operated in an inert and/or vacuum environment for separation ofliquid metal from the metal powder and salt leaving principally salt andmetal powder substantially free of liquid metal, transferring the saltand metal powder substantially free of liquid metal to a second vesseloperated in an inert environment, and thereafter treating the salt andmetal powder to produce passivated metal powder substantially free ofsalt and liquid metal.
 2. The method of claim 1, wherein the inertenvironment is an argon atmosphere.
 3. The method of claim 1, whereinthe salt and metal powder are crushed to form clumps having diametersless than about five centimeters prior to passivation.
 4. The method ofclaim 1, wherein the liquid metal is separated from the salt and metalpowder in the first vessel both as a liquid and as a vapor.
 5. Themethod of claim 4, wherein the liquid metal vapor from the first vesselis transferred to a condenser operated in an inert environment.
 6. Themethod of claim 4, wherein the liquid metal is an alkali or an alkalineearth metal or mixtures thereof.
 7. The method of claim 6, wherein thesalt is a halide.
 8. The method of claim 7, wherein the metal powder istitanium or a titanium alloy.
 9. The method of claim 8, wherein thetitanium or titanium alloy is CP 1 to CP
 4. 10. The method of claim 9,wherein the metal powder has diameters in the range of from about 0.1 toabout 10 microns.
 11. The method of claim 1, wherein passivation occurson a conveyor.
 12. The method of claim 11, wherein the metal powder iscontinuously cooled and passivated.
 13. The method of claim 1, whereinthe environments of the first and second vessels are protected fromcontamination by oxygen during the production of metal powdersubstantially free of salt and liquid metal.
 14. A method of separatingmetal powder from a slurry of liquid metal and metal powder and saltformed by introducing a metal halide vaporsubsurface of a liquid metalcausing an exothermic reaction producing salt and metal powder with theliquid metal being present in excess of the stoichiometric amountrequired, comprising introducing the slurry into a firstvessel operatedin an inert and/or vacuum environment for filtration and vaporization ofliquid metal from the metal powder and salt leaving principally salt andmetal powder substantially free of liquid metal, transferring the liquidmetal vapor to a condenser operated in an inert environment to convertthe liquid metal vapor to a liquid to be recycled for production ofadditional metal powder, transferring the salt and metal powdersubstantially free of liquid metal to a second vessel operated in aninert environment, and thereafter treating the salt and metal powder toproduce passivated metal powder substantially free of salt and liquidmetal.
 15. The method of claim 14, wherein the slurry is heated in thefirst vessel by contact with a heat exchanger internal to the firstvessel having heat exchange fluid pumped therethrough.
 16. The method ofclaim 14, wherein the liquid metal vapor from the first vessel is cooledby contact with heat exchanger internal to the condenser having a heatexchange fluid pumped therethrough.
 17. The method of claim 14, whereinthe first vessel is heated by both an internal and an external heatexchanger.
 18. The method of claim 14, wherein the slurry is introducedinto the interior of a candle filter in the first vessel with liquidmetal flowing through the candle filter and out of the first vessel. 19.The method of claim 14, wherein the inert environment for the first andsecond vessels is an argon atmosphere.
 20. The method of claim 19,wherein the condenser is operated in an argon atmosphere.
 21. The methodof claim 14, wherein the environments of the first and second vesselsare protected from contamination by oxygen during the production ofmetal powder substantially free of salt and liquid metal.
 22. A systemfor separating metal powder from a slurry of liquid metal and metalpowder and salt formed by introducing a metal halide vapor subsurface ofa liquid metal causing an exothermic reaction producing salt and metalpowder with the liquid metal being present in excess of thestoichiometric amount required, comprising a first inerted vessel incommunication with a heater and a filter for filtering liquid metal fromthe slurry and for heating liquid metal to vaporize the liquid metalfrom the salt and metal powder forming a filter cake of salt and metalpowder, an inerted condenser in communication with said first vessel forreceiving metal vapor and converting same to liquid metal, a secondinerted vessel in valved communication with said first inerted vesselfor receiving filter cake therefrom; a crusher in or in communicationwith said second inerted vessel for crushing the filter cake; a coolingand passivating station for receiving crushed filter cake, and a valvemechanism intermediate said first and second vessel and between saidsecond vessel and said cooling and passivating station to prevent airfrom contaminating said first and second vessels during transfer offilter cake from said first vessel to said cooling and passivatingstation.
 23. The system of claim 22, wherein said heater incommunication with said first inerted vessel is interior of said vessel.24. The system of claim 23, wherein said heater interior of said inertedfirst vessel is in communication with a source of heat exchange fluidwhich optionally is dedicated to said heater.
 25. The system of claim22, wherein said filter in communication with said first inerted vesselis interior of said vessel.
 26. The system of claim 25, wherein saidfilter is a filter forming an annulus with said first inerted vesselinto which liquid metal flows, and further including a conduit incommunication with said annulus for transferring liquid metal from saidfirst inerted vessel to an inerted liquid metal reservoir.
 27. Thesystem of claim 22, wherein said first and second inerted vessels areinerted with argon.
 28. The system of claim 27, wherein said condenseris inerted with argon.
 29. The system of claim 28, wherein said inertedcondenser is in communication with an argon inerted reservoir for liquidmetal formed from condensed metal vapor.
 30. The system of claim 22,wherein said condenser is in communication with a source of heatexchange fluid which optionally is dedicated to said condenser.
 31. Thesystem of claim 22, wherein said valve intermediate said first andsecond inerted vessel is hinged to open into said second inerted vessel.32. The system of claim 22, wherein said first and second vessel areintegral.